Small animal or laboratory animal research is a cornerstone of modem biomedical advancement. Research using small animals enables researchers to understand complex biological mechanisms, to understand human and animal disease progression, and to develop new drugs to cure or alleviate many human and animal maladies. Small animal research is important in many areas of biomedical research including neurobiology, developmental biology, cardiovascular research and cancer biology.
In many areas of biomedical research, accurately determining blood flow characteristics through a given organ or structure is important. For example, in the field of oncology, determination of blood flow within a tumor can enhance understanding of cancer biology and, since a tumor needs blood to grow and metastasize, help identify and develop anti-cancer therapeutics.
Color flow imaging systems estimate blood velocity by measuring the time, or frequency phase shift between backscattered signals. Color flow imaging of blood velocity in small animals such as mice and in humans has been accomplished by sweeping the transducer over a region of interest. This technique, however, has limitations including tissue clutter artifacts that are induced by the sweep velocity, which limits the ability to detect low flow rates. Other limitations include spatio-temporal decorrelation artifacts that occur when visualizing pulsatile flow, particularly if the pulse frequency is large relative to the sweep frequency of the probe. Moreover, an additional limitation includes limited accuracy of flow velocity estimation because of the number of radio frequency (RF) data lines acquired per location.